remove nullable from PollRepository return types

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/java/com/nextcloud/talk/polls/repositories/PollRepository.kt

@@ -33,11 +33,11 @@ interface PollRepository {
         options: List<String>,
         resultMode: Int,
         maxVotes: Int
-    ): Observable<Poll>?
+    ): Observable<Poll>
 
-    fun getPoll(roomToken: String, pollId: String): Observable<Poll>?
+    fun getPoll(roomToken: String, pollId: String): Observable<Poll>
 
-    fun vote(roomToken: String, pollId: String, options: List<Int>): Observable<Poll>?
+    fun vote(roomToken: String, pollId: String, options: List<Int>): Observable<Poll>
 
-    fun closePoll(roomToken: String, pollId: String): Observable<Poll>?
+    fun closePoll(roomToken: String, pollId: String): Observable<Poll>
 }

app/src/main/java/com/nextcloud/talk/polls/repositories/PollRepositoryImpl.kt

@@ -45,7 +45,7 @@ class PollRepositoryImpl(private val ncApi: NcApi, private val currentUserProvid
         resultMode: Int,
         maxVotes:
             Int
-    ): Observable<Poll>? {
+    ): Observable<Poll> {
         return ncApi.createPoll(
             credentials,
             ApiUtils.getUrlForPoll(
@@ -71,7 +71,7 @@ class PollRepositoryImpl(private val ncApi: NcApi, private val currentUserProvid
         ).map { mapToPoll(it.ocs?.data!!) }
     }
 
-    override fun vote(roomToken: String, pollId: String, options: List<Int>): Observable<Poll>? {
+    override fun vote(roomToken: String, pollId: String, options: List<Int>): Observable<Poll> {
 
         return ncApi.votePoll(
             credentials,